Contributions of Glucose and Hemoglobin A1c Measurements in Diabetes Screening.

OBJECTIVES: Given the long-term consequences of untreated diabetes, patients benefit from timely diagnoses. Payer policies often recognize glucose but not hemoglobin A1c (HbA1c) for diabetes screening. This study evaluates the different information that glucose and HbA1c provide for diabetes screening. METHODS: We conducted a retrospective review of national clinical laboratory testing during 2020 when glucose and HbA1c were ordered for routine diabetes screening, excluding patients with known diabetes, out-of-range glucose, or metabolic syndrome. RESULTS: Of 15.47 million glucose and HbA1c tests ordered simultaneously, 672,467 (4.35%) met screening inclusion criteria; 116,585 (17.3%) were excluded because of diabetes-related conditions or the specimen was nonfasting, leaving 555,882 result pairs. More than 1 in 4 patients 60 years of age or older with glucose within range had an elevated HbA1c level. HbA1c claims were denied more often for Medicare beneficiaries (38,918/65,273 [59.6%]) than for other health plans combined (23,234/291,764 [8.0%]). CONCLUSIONS: Although many health plans do not cover HbA1c testing for diabetes screening, more than 1 in 4 glucose screening patients 60 years of age or older with an in-range glucose result had a concurrent elevated HbA1c result. Guideline developers and health plans should explicitly recognize that glucose and HbA1c provide complementary information and together offer improved clinical utility for diabetes screening.